Electric motors have been proposed for driving the plates, such as direct current, alternate current or three-phase motors. These motors can be of the synchronous, asynchronous or stepping types. These electric motors are firmly connected to the plate, such as by means of a so-called coupling flange and a plate support, which, by being connected between the end of the motor shaft and the plate, provide a (rotatably integral) serial connection between the motor shaft and the plate.
Said alignment means for controlling the angular position of the containers to be labelled can comprise optical sensors, such as photocells or video cameras suitable to detect a mark (such as a line, a projection, or a groove) provided in each container or process more complex reference images. Alternatively, the alignment means for the containers to be labelled can comprise mechanical devices suitable to align the container at an angle relative to the plate, in order to allow controlling the angular position of the container by monitoring and piloting the angular position of the motor shaft connected to the plate.
The application of reference marks on the visible surface of bottles has proved disadvantageous, both in terms of visual appearance, and because particular shapes of the bottles, such as very salient edges, etc., are likely to affect mark detection in a negative manner. It is thus desired to be able of arranging the reference marks on the bottom wall of the bottle. This bottom wall is substantially invisible when the bottle is being used and normally has a shape that is sufficiently even to avoid affecting the control of the angular position in a negative manner.
However, as in the case of labelling machines to which the present invention is referred, the bottom wall of the bottle is not always accessible, because the space below this bottom wall is occupied by the plate and drive motor associated with the plate.
This prevents the alignment means from having direct axial (either optical or mechanical) access to the bottom wall of the bottle.
A coaxial arrangement of the motor relative to the plate thus requires a crosswise access by the alignment means, and a direct, i.e. axial, access by the alignment means to the bottom wall of the container inevitably implies an eccentric positioning of the motor. Both solutions are bulky and require complex drive mechanisms.
It is accordingly the object of the present invention to provide a motor for a plate having such characteristics as to allow the same to be positioned relative to the plate and coupled thereto in a coaxial manner, while allowing the alignment means to have direct access to the bottom wall of the bottle.